Development of the non-invasive stable 35% xenon inhalation computerized tomographic method (XesCTCBF) will continue in baboons and application of the method to carefully selected human volunteers and patients with stroke, subarachnoid hemorrhage, intracerebral hematoma, brain tumor will progress. Effects of activation studies and sleep on local cerebral blood flow will be measured in 3 dimensions with a resolution of less than 1 cu. cm. The effects of normal aging on CBF will be continued in a prospective study of 300 normal volunteers and the modification of CBF by risk factors for atherosclerosis, TIAs and Stroke will continue to be documented. Studies of cerebral edema due to stroke will be continued in experimental animals together with neuropharmacological studies of cerebrovascular control mechanisms. The relationship of Ca 2 ions to cell function will continue. Double blind clinical studies of treatment of migraine with a drug (Nimidopine blocking Ca 2 ion entry into cerebrovascular smooth muscle will be carried out and studies of cerebral atherogenesis will proceed.